A vector-valued function on \(G\)  that is covariant with respect to both left and right regular actions of \(K\)  is uniquely specified by the values it takes on \(A\) . Therefore, the \(K\) -spherical functions may be considered as functions of two variables \(u_1\) , \(u_2\) , [1]}, [2]}. This is in agreement with the fact that four-point functions in a conformal field theory depend on two cross ratios.
